Preparation of polyethylene-graft-clay nanocomposites using Friedel–Crafts alkylation reaction as a new method

Abstract

The main objective of this study was chemical grafting of polyethylene (PE) chains onto clay surfaces in PE/clay nanocomposites. Clay (Cloisite 30B) particles were successfully modified using a laboratory-synthesized carboxylic acid end-functionalized polystyrene (F-PS) and a commercial styrene–maleic anhydride copolymer (SMA). SMA showed higher grafting efficiency than F-PS. It is related to lower molecular weight and higher compatibility of SMA with Cloisite 30B particles. Both modified Cloisite 30B particles were used in preparation of PE nanocomposites where AlCl3 catalyst was used for chemical grafting of PE chains onto polystyrene (PS) or SMA chains, pendant from the clay particles surfaces. Using AlCl3 increased the storage modulus and decreased the damping factor, particularly at low-frequency ranges. It was related to the chemical grafting of the PE chains onto the PS segments of the SMA copolymer and the PS chains of F-PS on the clay particle surfaces via Friedel–Crafts alkylation reaction. Catalyzed nanocomposites showed better clay dispersion than those of the plain nanocomposites. It is believed that chemical grafting of PE chains onto clay particles surfaces provided effective stress transfer from PE matrix to clay tactoids resulting in delamination and higher degree of clay exfoliation.